46 



Rev. S. Haughton on the Law of Fatigue. [Nov. 18, 



The calculated values of n were found from equation (2), using the 

 values 



a=3-9 lbs., 

 A=5737, 



which were obtained from the principle of least variation of A, or 



—— = minimum. 

 A 



In the accompanying diagrams I, & II. (p. 45) I have plotted the cubical 

 hyperbola represented by equation (2), and also the several observations, 

 which lie sufficiently near the curve to justify me in considering the law 

 of fatigue to be a first approximation to one of the fundamental laws of 

 muscular action. I have elsewhere * shown that the law of fatigue corre- 

 sponds with other experiments based on different data. 



If we consider the useful work only, we have, from equation (2), 



useful work =ivn= 



Aw 



(w + af 



(3) 



This equation represents a cuspidal cubic, whose ordinate has a maxi- 

 mum value, when w=a= half the weight of the arm. 



The foregoing observations are in accordance with this deduction, as 

 may be seen from Table III. 



Table III. Useful Work. 



No. 



w. 



wn (20 experi- 

 ments). 



wn (Mr. Warren). 





lbs. 







1. 



2-56 



338 



358 



2. 



4-25 



372 



387 



3. 



5-87 



277 



370 



4. 



6-87 



276 



295 



5. 



7-75 



268 



310 



6. 



9-75 



264 



312 



7. 



14-00 



241 



250 



* Principles of Animal Mechanics. London, 1873. 



